As an animal that spends much of its time hammering its head against trees at a force of 1,200 g’s, it’s unsurprising that many sports companies have looked to the woodpecker’s biology to design better safety equipment and helmets for football players, in order to protect them against brain damage.

But weirdly, no one had actually thought to find out if by hitting their head against a tree at 24 kilometers (15 miles) per hour, woodpeckers are actually harming their brains. Interestingly, new research has found that the birds – which experience 10 times more force against their noggins than NFL players – show the build-up of a protein associated with chronic traumatic encephalopathy (CTE) in humans, a degenerative brain disease seen in many athletes.

This does not mean that the birds get brain damage, but it does mean that the picture is slightly more complicated than we originally thought.

The team turned to the preserved brains of woodpeckers to see if they could identify any signs of brain injury in the animals, and compared them to the brains of birds that do not bash their heads against solid wood for a living. What they found, published in PLOS ONE, was really interesting, but also unexpected.

It turns out that in the woodpecker brains that the researchers were able to accurately assess, there were elevated levels of tau proteins wrapped around their neurons. But while this is indicative of brain damage and injury in humans, there was nothing to suggest that the same is true for the woodpeckers.

“The earliest woodpeckers date back 25 million years – these birds have been around for a long time,” explained Peter Cummings, who coauthored the paper. “If pecking was going to cause brain injury, why would you still see this behavior? Why would evolutionary adaptations stop at the brain? There’s possibility that the tau in woodpeckers is a protective adaptation and maybe not pathological at all.”

High levels of tau in the brains of NFL players are usually a sign that a player is suffering from CTE, but that doesn’t mean that tau is necessarily a bad thing. In fact, rather paradoxically, in healthy brains the protein plays a critical role in protecting neurons. It coats the cells, helping to stabilize the neurons and preventing them from being pushed out of shape. It is only when tau levels start to increase, usually in response to blunt head trauma, that rather than helping neurons, tau begins to interfere with them and disrupt their signals.

This is true in humans at least. The fact that the woodpeckers showed elevated tau, but seemingly no other indications that they were suffering brain injury raises interesting questions about the role of the protein in the brain, and how it affects professional athletes.